LOWELL — Two brothers are dead after a shooting on Andrews Street early Sunday, authorities said.

Police responded the home when someone called police about 2:30 a.m. asking for help. When officers arrived they found Keith Callahan, 35, and Joseph Callahan, 29, suffering from gunshot wounds, according to a statement from Middlesex District Attorney Marian Ryan and Lowell Police Superintendent William Taylor.

Keith Callahan died at the scene, and Joseph Callahan was taken to Lowell General Hospital, where he later died, authorities said.

No arrests have been made, but Sunday night police asked the public to help identify a suspect.

Ryan’s office said investigators are looking for a thin 5-foot 6-inch man between 25 and 35 years old.

Prosecutors released a sketch of the suspect, who has a goatee that extends a half-inch below his chin and dark hair that he wears in a short ponytail. He was seen wearing a white T-shirt and jeans.

Lowell police and State Police assigned to Ryan’s office are investigating the killings, authorities said. Autopsies on both men will be performed by the office of the state’s chief medical examiner.

A woman answering the phone at the Callahan family home in Lowell had no comment.

There was no answer at the phone listed for the residents of the Andrews Street home.

Outside of the home where the shooting occurred on Sunday afternoon, a spontaneous memorial for the brothers included a stuffed puppy with the handwritten messages “R.I.P” and “LOVE U” and a single yellow rose.

Friends of the family later poked a stuffed lion through the chain-link fence beneath police tape.

Residents on the block of weathered two-family homes where the shooting occurred said they believed the shots may have been fired during a party early Sunday, but they heard no commotion.

“I know they party a lot over there,” said Michelle Denny, 50, who lives a few houses down. “They have big cookouts, and have bonfires.”

Denny said she heard what she thought were fireworks as she waited for her daughter to return home early Sunday. Police arrived moments later, shining spotlights through the windows at the Andrews Street home, she said.

She described seeing a tall man being taken from the house on a stretcher.

Carrie Lincoln, 37, said she heard the shots as she lay awake Sunday morning. She feared for herself and her young children.

“I had heard a gunshot before so I knew what it was,” she said.

“I’m worrying about my children running outside. It’s not the first time I’ve heard gunshots around here.”

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